The present invention relates to an ink jet recording apparatus provided with an ink jet recording head for use in forming images on recording paper by ejecting ink drops from nozzle orifices, and a flushing region disposed on a head moving path for receiving the ink drops ejected when a flushing driving signal is supplied to the recording head, and more particularly to an ink jet recording apparatus provided with an ink collecting unit for effectively collecting unnecessary mist (atomized ink) resulting from fine ink drops produced during the flushing operation.
The present invention relates to an ink jet recording apparatus provided with an ink collecting unit for effectively collecting unnecessary mist (atomized ink) resulting from ink drops produced at the time of inspecting an ink ejecting condition so as to detect any unoperating nozzle by checking the presence or absence of the ink drops ejected from nozzle orifices of a recording head.
The present invention relates to an ink jet recording apparatus in which at the time of inspecting an ink ejecting condition so as to detect any unoperating nozzle, it is ensured that such an unoperating nozzle can be detected and an inspecting method used in the apparatus.
Ink jet recording apparatus are now widely used for printing including color printing partly because relatively less printing noise is produced and partly because high-density small dots are formable. The ink jet recording apparatus of this type is generally provided with an ink jet recording head mounted on a carriage and used for scanning recording paper in its width direction and a paper feeder for moving the recording paper in a direction perpendicular to the scanning direction of the recording head. Then recording is performed by ejecting ink drops from the recording head onto the recording paper according to printing data.
Further, not only text printing with black ink but also full-color printing can be performed by continuously supplying, to the recording head, black ink and three kinds of color ink of yellow, cyan and magenta, for example, by varying the ejection ratios of these different kinds of color ink.
In view of the fact that the ink jet recording apparatus like this is used for printing by ejecting the ink pressurized in a pressure generating chamber from nozzle orifices as ink drops onto recording paper, there may develop poor-quality printing due to a rise in ink viscosity originating from evaporation of an ink solvent from the nozzle orifices, solidification of ink, adhesion of dust, mixture of bubbles and so forth. For this problem of poor-quality printing, the ink jet recording apparatus is provided with a head cap for sealing the nozzle orifices of the recording head and a wiper for cleaning the nozzle forming face as occasion demands while printing is not performed.
The head cap serves as not solely a cover member for preventing the ink of the nozzle orifices of the recording head from being dried out while printing is suspended but also what receives negative pressure from a suction pump when the nozzle orifices are clogged so as to suck and discharge the ink from the nozzle orifices whereby to solve the problem of clogging due to the solidification of ink in the nozzle orifices and the problem of an unsatisfactory ejection of ink resulting from the introduction of bubbles into an ink channel.
The process of forcing the ink to be sucked and discharged so as to solve the problems of clogging of the recording head and of the introduction of bubbles into the ink channel is called a cleaning operation, which is performed, for example, in case where printing is performed again after a long suspension of the operation of the recording apparatus or in case where the user depresses, for example, a cleaning switch after recognizing the deterioration of printed image quality. The cleaning operation is accompanied with the operation of wiping the nozzle forming face of the recording head with the wiper formed of an elastic plate of rubber or the like after the ink is caused to be sucked and discharged from the recording head.
A function of causing ink drops to be ejected by applying a driving signal to the recording head is also retained, though the driving signal is irrelevant to printing, which is called a flushing operation. The flushing operation is performed periodically to recover irregular meniscuses produced in the vicinity of the nozzle orifices of the head through the wiping operation of the wiper and to prevent any nozzle orifice ejecting few ink drops from being clogged with extremely viscous ink while printing is performed.
FIG. 5 shows an example of a conventional ink jet recording apparatus so arranged that during the flushing operation, ink drops are ejected toward a flushing region formed on a head moving path.
In FIG. 5, reference numeral 1 denotes a carriage so arranged as to be guided by a guide shaft 4 supported by left and right frames 2 and 3 via a timing belt driven by a carriage motor (not shown) and reciprocated in the axial direction of the guide shaft 4.
The carriage 1 is loaded with an ink jet recording head 5 directed downward, a detachable black ink cartridge 6 and a detachable color ink cartridge 7 for supplying ink to the recording head 5 being also mounted thereon. Under the recording head 5 lies a platen 8 that extends in the scanning direction of the recording head 5 so that recording paper 9 mounted on the platen 8 can be moved by a paper feeder (not shown) successively in a direction perpendicular to the scanning direction of the recording head 5.
Reference numeral 10 denotes a head cap that is disposed in a non-printing region (home position). When the recording head 5 is placed just above the head cap 10, it is moved upward so as to seal the nozzle forming face of the recording head 5. A suction pump 11 for providing negative pressure to the internal space of the head cap 10 is also disposed under the head cap 10.
As described above, the head cap 10 serves as not solely a cover member for preventing the nozzle orifices of the recording head 5 from being dried out during the suspension of operation of the recording apparatus but also a cleaner for causing ink to be sucked and discharged by making the negative pressure from the suction pump 11 act on the recording head 5.
Further, a wiper 12 formed of an elastic plate of rubber or the like is disposed in the vicinity of the head cap 10 and the operation of wiping the nozzle forming face of the recording head 5 is performed thereby when the carriage 1 moves toward the head cap 10.
On the other hand, a flushing region 13 is formed in the vicinity of the other end opposing to the head cap 10 via the central printing region, The flushing region 13 is formed of an aperture in such a manner as to pass through the platen 8. Further, part of a waste-ink absorber 14 for absorbing the ink discharged via the pump 11 from the head cap 10 is disposed in the inner base portion of the aperture forming the flushing region 13. The absorber 14 extends along the platen 8 and is contained in a casing member, that is, a waste-ink tank 15.
In the recording apparatus, flushing is performed periodically as described above to prevent an unsatisfactory ejection of ink resulting from an increase in ink viscosity in an unused nozzle while printing is performed. Flushing is performed in each nozzle orifice with a frequency of about tens of shots every several seconds on average. The flushing operation may be performed with from thousands to tens of thousands shots from each nozzle periodically, depending on the timing after the cleaning operation for the prevention of mixture of colors is performed, the timing in the beginning of printing or while printing is performed.
When the aperture is formed in the platen 8 as the flushing region 13 of FIG. 5, the distance from the nozzle forming face of the recording head 5 up to the waste-ink absorber 14 is approximately tens of millimeters and the flying distance of ink inevitably increases. Consequently, some of ink drops ejected from the nozzle orifices of the recording head are reduced to mist (atomized ink) because of air resistance and become afloat as shown by arrows and the problem in this case is that the inside and outside of the apparatus, to say nothing of recording paper, are contaminated.
In order to prevent the occurrence of such a problem as mentioned above, the provision of the waste-ink absorber in a position close to the recording head may be considered. However, there normally exist mechanisms such as the paper feeding roller in a portion opposite to the head within the traveling range of carriage, so that a sufficient capacity is actually unavailable. Moreover, the ink drops ejected from the nozzle orifices are electrically charged to no small extent and affected by the static electricity generated in the driving portion within the recording apparatus and also accelerated by an air flow because of a ventilation fan disposed so as to suppress a temperature rise within the apparatus or an air flow accompanying the movement of the carriage. Therefore, the problem of contaminating the inside and outside of the recording apparatus as well as the recording paper still remains to be solved. In the recent recording apparatus so arranged as to minimize the amount of each ink drop under control to realize high image quality in particular, the problem like this appears conspicuous.
Due to a rise in ink viscosity and the solidification of ink originating from the evaporation of the ink solvent from the nozzle orifices and the introduction of bubbles into the nozzle orifices, the problem of causing ink drops to be unsatisfactorily ejected is still left unsolved. In case where the situation above is produced, so-called dot omission found in printed images results in deteriorating their quality and there has been proposed a recording apparatus provided with an ejecting condition inspector (ejecting condition detector) for optically inspecting whether the dot omission occurs.
The ejecting condition inspector essentially consists of a combination of a light emitting element for emitting light beams and a light receiving element for receiving the light beams from the light emitting element and operates to emit the light beams sequentially in a manner crossing the flying courses of the ink drops ejected from the nozzle orifices of the recording head. While controlling the ejection of ink drops from the nozzle orifices of the recording head in time series, the ejecting condition detector detects the quantity of light in the light receiving element whereby to specify the unsatisfactory ejecting condition of ink drops in each of the nozzle orifices.
As the above-described optical detector (ejecting condition detector) is used to inspect the ejecting condition in a manner corresponding to each of the many nozzle orifices thus oriented, the light emitted from a light emitting module to a light receiving module is converged into what has a very small diameter (1 mm or less).
On the other hand, an ink ejection similar to the above-described flushing operation is performed from each of the nozzle orifices (nozzle-forming face) and the ink drops thus ejected drop in the gravitational direction within the ejecting condition detector (ejecting region). However, most of the ink drops are changed into ink mist (atomized ink) as in the above-described case and become afloat in the ejecting condition detector. As a result, the light emitting and light receiving modules tend to become easily contaminated by the ink mist and the problem in this case is that reliability from the standpoint of the detection of the ejecting condition lowers.
Moreover, the ejecting condition may be detected so as to detect any unoperating nozzle orifice after the cleaning operation is performed. In making this inspection, there is found a nozzle orifice whose operation is unstable among the nozzle orifices immediately after the cleaning operation is performed though the reason for this is not obvious and it has not been ensured that such an unoperating nozzle orifice can be detected.
More specifically, because ink is still unstably ejected from the unoperating nozzle orifice at the time of inspecting the ejection of ink drops, that nozzle orifice cannot be detected as an unoperating nozzle orifice and the problem in this case is that satisfactory printing is unavailable as no stable ejection is obtainable when the printing is performed thereafter.
A first object of the present invention made in view of the foregoing problems is to provide an ink jet recording apparatus equipped with an ink collecting unit capable of effectively collecting ink mist floating in the form of fine drops while a flushing operation is performed.
A second object of the present invention made with close attention directed to the foregoing problems is to provide an ink jet recording apparatus capable of preventing a light emitting module and a light receiving module from being contaminated by ink mist and also capable of improving reliability from the standpoint of the detection of an ejecting condition.
A third object of the present invention made with close attention directed to the foregoing problems is to provide an ink jet recording apparatus capable of ensuring that an ejection of ink drops is inspected after a cleaning operation is performed and to provide a method of inspecting an ejection of ink drops.
In order to accomplish the first object, according to the invention, there is provided an ink jet recording apparatus, comprising:
a carriage, which moves in a widthwise direction of recording paper;
an ink jet recording head, mounted on the carriage and provided with nozzle orifices for ejecting ink drops to form an image on the recording paper; and
an ink collecting unit, placed on a moving path of the recording head for receiving ink drops ejected from the recording head to which a flushing drive signal is supplied; the ink collecting unit including: an unit box formed with an aperture through which the ink drops ejected from the recording head to which the flushing drive signal is supplied; an air flow passage; and a ventilation fan, placed on the way of the air flow passage or a termination end portion of the air flow passage.
Here, it is preferable that the air flow passage extends meandering in a vertical direction.
In order to accomplish the first object, according to the invention, there is also provided an ink jet recording apparatus, comprising:
a carriage, which moves in a widthwise direction of recording paper;
an ink jet recording head, mounted on the carriage and provided with nozzle orifices for ejecting ink drops to form an image on the recording paper; and
an unit box, placed on a moving path of the recording head for receiving ink drops ejected from the recording head to which a flushing drive signal is supplied, the unit box formed with an aperture through which the ink drops ejected from the recording head to which the flushing drive signal is supplied, and an air flow passage, which extends meandering in a plurality of directions.
Here, it is preferable that the air flow passage extends meandering in a vertical direction.
In order to accomplish the second object, according to the invention, there is provided an ink jet recording apparatus, comprising:
a carriage, which moves in a widthwise direction of recording paper;
an ink jet recording head, mounted on the carriage and provided with nozzle orifices for ejecting ink drops to form an image on the recording paper;
an ejecting condition detector, placed on a moving path of the recording head, the ejecting condition detector including:
a light emitting module and a light receiving module, which detects an ejecting condition of ink drops ejected from the nozzle orifices; and
an ink ejecting region, placed between the light emitting module and the light receiving module for receiving ink drops ejected from the recording head; and
a unit box, which faces to the ink ejecting region for collecting ink in the ink ejecting region, the unit box formed with an air flow passage therein.
Preferably, the unit box is formed with an aperture through which ink drops ejected from the recording head to which a flushing drive signal is supplied. Here, the air flow passage extends meandering in a vertical direction.
Preferably, the unit box is provided with a ventilation fan disposed on the way of the air flow passage or a termination end portion of the air flow passage.
In order to accomplish the first and second objects, it is preferable that the air flow passage extends from the aperture while meandering in a gravitational direction and a counter-gravitational direction.
Here, it is preferable that the air flow passage extends from the aperture toward a conter-gravitational direction while an ink collecting space is formed so as to extend from the aperture in the gravitational direction. Further, the ink collecting space has a bottom formed with a discharging port from which collected waste ink is discharged.
On the other hand, preferably, a plurality of plate members are provided in the air flow passage so as to increase a surface area of the air flow passage. In this case, the plate members are alternately extended from side walls of the air flow passage to constitute an air flow passage meandering in a horizontal direction.
Here, it is preferable that a leading end portion of each plate member is slanted toward the gravitational direction. Further, the plate members are provided in the air flow passage which extends in the counter-gravitational direction.
Preferably, each bottom portion of the air flow passage meandering in the vertical direction has a guide port communicated with the ink collecting space for guiding waste ink thereto.
Preferably, an air filter is disposed in a part of the air flow passage. Here, it is preferable that the air filter is disposed in the vicinity of the ventilation fan.
Preferably, the unit box includes: a side wall; a peripheral wall, which extends perpendicularly from the side wall to define a box body in which a side opposing to the side wall is opened; internal walls, which define the air flow passage; and a sealing member, which closes the opened side of the box body.
Here, it is preferable that a thermally fusible member is provided as the sealing member.
In the ink jet recording apparatus provided with the ink collecting unit (unit box) as described above, the ink drops ejected from the nozzle orifices of the recording head positioned in the flushing region or the ink drops ejected from the nozzle orifices of the recording head positioned in the ejecting region of the ejecting condition detector are immediately introduced into the ink collecting unit through the aperture of the ink collecting unit.
Further, the ink drops ejected from the nozzle orifices of the recording head are collected in the collecting space formed in the vicinity of the aperture of the unit box in the gravitational direction. Then the waste ink collected in the collecting space is discharged outside through the discharging port formed in the bottom portion of the collecting space.
On the other hand, even though some of the ink drops are changed into mist while such ink drops are flying after being ejected into the aperture in the unit box, the mist is surely taken into the unit box in the air flow passage of the unit box or by the air flow produced by the ventilation fan disposed in the termination end portion thereof.
The mist taken into the unit box is carried on the air flow produced by the ventilation fan and passed through the continuous air flow passage meandering in the gravitational and counter gravitational directions while being captured by contact with the inner wall face of the air flow passage.
In this case, since the contact area of the ink mist can substantially be increased by the plate members disposed in the air flow passage, the collection of the ink mist can also be increased.
Moreover, the alternate provision of the plate-like bodies in the air flow passage permits the air flow passage to be formed in a manner horizontally meandering, whereby the path of the moving air flow becomes more complicated, thus improving the collection further.
In the ejecting condition detector having the ink collecting unit for collecting the ink drops, it is preferable that a plurality of ink shading walls, each having a light transmission hole, are disposed between the light emitting module and the light receiving module. With this arrangement, the ink ejected from the nozzle forming face of the recording head is shaded by the ink shading walls.
Here, it is preferable that a plurality of partition walls are disposed between a pair of ink shading walls which define the ink ejecting region. With this arrangement, a duct for distributing ink is formed by the partition walls and the ink shading walls and the ink drops flow down in the duct.
Further, it is preferable that a cutout portion is formed on a head-side edge portion of each partition wall to form an air flow in the vicinity of the light transmission hole. With this arrangement, the ink drops ejected from the nozzle forming face of the recording head are carried on the air flow in the vicinity of the light transmission hole and passed through the cutout and flow into the ejecting region.
Still further, each partition wall is formed with an ink guide for guiding ink from the outside of the ink ejecting region to the inside of the ink ejecting region. With this arrangement, ink drops outside the ejecting region are guided into the ejecting region along the ink guide.
Preferably, an ink discharging port is formed in each internal space defined by the respective ink shading walls for discharging ink therefrom. With the arrangement, when the ink drops ejected from the nozzle forming face of the recording head flow into the internal space of the ejecting condition detector at the time of detecting the ejecting condition, the ink drops are discharged outside from the internal space via the ink discharging port.
Therefore, both modules are prevented from being contaminated by ink mist as the ink mist does not float in the ejecting condition detector and reliability from the standpoint of the detection of the ejecting condition is enhanced.
Here, the internal space is placed in the vicinity of the light emitting module. With this arrangement, when ink mist flows from the light transmission hole into the internal space near the light emitting module, the ink mist is discharged outside from the internal space via the ink discharge port.
Preferably, a size of the light transmission hole situated downwards is smaller than a size of the light transmission hole situated upwards. With this arrangement, the inflow of the ink drops ejected from the nozzle forming face of the recording head into the light transmission holes is gradually suppressed along the gravitational direction.
Preferably, a recessed portion is formed on a head-side edge portion of each ink shading wall. With this arrangement, when the ink drops ejected from the recording head flow into the recessed portion and drop, the flowing of the ink drops into the light transmission hole in the vicinity of both modules is blocked.
In order to accomplish the third object, according to the invention, there is provided an ink jet recording apparatus, comprising:
a carriage, which moves in a widthwise direction of recording paper;
an ink jet recording head, mounted on the carriage and provided with a nozzle forming face on which nozzle orifices are formed;
a head driver, which drives the recording head so as to eject ink drops from the nozzle orifices to form an image on the recording paper;
a scanning driver, which moves the recording head in a main scanning direction;
an ejecting condition detector, which performs an inspection in which it is detected whether ink drops are ejected from the nozzle orifices;
a cleaner, which performs a cleaning operation in which negative pressure is applied to the nozzle orifices to discharge ink therefrom and the nozzle forming face is wiped with a wiper; and
a controller, which supplies a flushing drive signal to the head driver to eject ink drops from the nozzle orifices, after the cleaner performs the cleaning operation and before the ejecting condition detector performs the inspection.
Preferably, when an unoperating nozzle is detected as a result of the inspection, the cleaner performs the cleaning operation, the controller then supplies the flushing signal to the recording head, and the ejecting condition detector then performs the inspection.
Preferably, the recording apparatus further comprises an ink collecting unit which faces to the ejecting condition detector and includes a unit box formed with an aperture through which ink drops ejected from the recording head to which the flushing drive signal is supplied, an air flow passage formed in the unit box, and a ventilation fan disposed on the way of the air flow passage or a termination end portion of the air flow passage.
Preferably, the controller supplies the flushing drive signal after the ejecting condition detector performs the inspection.
Preferably, the controller displays an error indication when a predetermined number of inspections are repeated by the ejecting condition detector. Here, the error indication is displayed on the recording apparatus or a host computer to which the recording apparatus is connected.
In order to accomplish the third object, according to the invention, there is also provided an inspection method used in a recording apparatus, comprising: a carriage, which moves in a widthwise direction of recording paper, an ink jet recording head, mounted on the carriage and provided with a nozzle forming face on which nozzle orifices are formed; a head driver, which drives the recording head so as to eject ink drops from the nozzle orifices to form an image on the recording paper, and a scanning driver, which moves the recording head in a main scanning direction, the method comprising the steps of:
performing a cleaning operation in which negative pressure is applied to the nozzle orifices to discharge ink therefrom and the nozzle forming face is wiped with a wiper;
supplying a flushing drive signal to the head driver to eject ink drops from the nozzle orifices, after the cleaning operation is performed; and
performing an inspection in which it is detected whether ink drops are ejected from the nozzle orifices, after the flushing operation is performed.
Preferably, the inspection method further comprises the steps of:
performing the cleaning operation when an unoperating nozzle is detected as a result of the inspection;
supplying the flushing drive signal to the head driver after the cleaning operation is performed; and
performing the inspection after the flushing operation is performed.
Preferably, the inspection method further comprises the step of supplying the flushing drive signal after the inspection is performed.
Preferably, the inspection method further comprises the step of displaying an error indication when a predetermined number of the inspections are repeated. Here, the error indication is displayed on the recording apparatus or a host computer to which the recording apparatus is connected.
Therefore, any unstable nozzle orifice, if any, can be shifted to either a inferior condition (unoperating condition) in which ink is not ejected completely during flushing or a condition in which ink is satisfactorily ejected. Consequently, the condition of the nozzle orifice is never changed after the inspection is made to ensure that the presence or absence of ink ejection is detected by the inspection. Non-conforming printing action is never caused thereafter.
When an unoperating nozzle is detected as a result of the inspection, since the cleaner performs the cleaning operation, the controller then supplies the flushing signal to the recording head, and the ejecting condition detector then performs the inspection again, the nozzle orifices can completely be restored to the normal condition, so that improved-quality printing can be attained.
Since the ink collecting unit is provided so as to face to the ejecting condition detector, the ink drops ejected from the nozzle orifices of the recording head positioned in the ejecting region of the ejecting condition detector are immediately introduced into the ink collecting unit through the aperture of the ink collecting unit. Even though some of the ink drops are changed into mist while such ink drops are flying after being ejected into the aperture in the unit box, the mist is surely taken and collected into the unit box in the air flow passage of the unit box or by the air flow produced by the ventilation fan disposed in the termination end portion thereof.
Ink viscosity may be prevented from increasing by supplying the flushing drive signal to the head driver to eject ink after the termination of inspection.
Moreover, an error may be displayed to warn the user that maintenance is needed in case where a predetermined number of inspections are repeated by the ejecting condition detector.